diff --git a/mio/lib/mio-chr.h b/mio/lib/mio-chr.h
index dc2cf13..ccd9f20 100644
--- a/mio/lib/mio-chr.h
+++ b/mio/lib/mio-chr.h
@@ -91,6 +91,11 @@ typedef enum mio_ooch_prop_t mio_bch_prop_t;
 	 ((c) >= 'A' && (c) <= 'F')? ((c) - 'A' + 10): \
 	 ((c) >= 'a' && (c) <= 'f')? ((c) - 'a' + 10): -1)
 
+#define MIO_ZDIGIT_TO_NUM(c,base) \
+	(((c) >= '0' && (c) <= '9')? ((c) - '0'): \
+	 ((c) >= 'A' && (c) <= 'Z')? ((c) - 'A' + 10): \
+	 ((c) >= 'a' && (c) <= 'Z')? ((c) - 'a' + 10): base)
+
 #if defined(__cplusplus)
 extern "C" {
 #endif
diff --git a/mio/lib/skad.c b/mio/lib/skad.c
index 16b6c40..e6fc2d7 100644
--- a/mio/lib/skad.c
+++ b/mio/lib/skad.c
@@ -184,13 +184,7 @@ static int uchars_to_ipv6 (const mio_uch_t* src, mio_oow_t len, struct in6_addr*
 
 		ch = *src++;
 
-		if (ch >= '0' && ch <= '9')
-			v1 = ch - '0';
-		else if (ch >= 'A' && ch <= 'F')
-			v1 = ch - 'A' + 10;
-		else if (ch >= 'a' && ch <= 'f')
-			v1 = ch - 'a' + 10;
-		else v1 = -1;
+		v1 = MIO_XDIGIT_TO_NUM(ch);
 		if (v1 >= 0)
 		{
 			val <<= 4;
@@ -294,13 +288,7 @@ static int bchars_to_ipv6 (const mio_bch_t* src, mio_oow_t len, struct in6_addr*
 
 		ch = *src++;
 
-		if (ch >= '0' && ch <= '9')
-			v1 = ch - '0';
-		else if (ch >= 'A' && ch <= 'F')
-			v1 = ch - 'A' + 10;
-		else if (ch >= 'a' && ch <= 'f')
-			v1 = ch - 'a' + 10;
-		else v1 = -1;
+		v1 = MIO_XDIGIT_TO_NUM(ch);
 		if (v1 >= 0)
 		{
 			val <<= 4;
diff --git a/mio/lib/utl.c b/mio/lib/utl.c
index 6b978f3..936d74d 100644
--- a/mio/lib/utl.c
+++ b/mio/lib/utl.c
@@ -1221,17 +1221,9 @@ mio_intmax_t mio_uchars_to_intmax (const mio_uch_t* str, mio_oow_t len, int opti
 	pp = p;
 	while (p < end)
 	{
-		if (*p >= '0' && *p <= '9') {
-			digit = *p - '0'; }
-		else if (*p >= 'A' && *p <= 'Z')
-			digit = *p - 'A' + 10;
-		else if (*p >= 'a' && *p <= 'z')
-			digit = *p - 'a' + 10;
-		else break;
-
+		digit = MIO_ZDIGIT_TO_NUM(*p, base);
 		if (digit >= base) break;
 		n = n * base + digit;
-
 		p++;
 	}
 
@@ -1315,17 +1307,9 @@ mio_intmax_t mio_bchars_to_intmax (const mio_bch_t* str, mio_oow_t len, int opti
 	pp = p;
 	while (p < end)
 	{
-		if (*p >= '0' && *p <= '9')
-			digit = *p - '0';
-		else if (*p >= 'A' && *p <= 'Z')
-			digit = *p - 'A' + 10;
-		else if (*p >= 'a' && *p <= 'z')
-			digit = *p - 'a' + 10;
-		else break;
-
+		digit = MIO_ZDIGIT_TO_NUM(*p, base);
 		if (digit >= base) break;
 		n = n * base + digit;
-
 		p++;
 	}